Cabin pressure control system



July 4, 1950 J. M. KEMPER CABIN PRESSURE CONTROL SYSTEM 2 Sheets-Sheet 1Filed Nov. 18, 1946 JAMES M. KEMPER J ATTORNEY July 4, 1950 K E2,513,332

CABIN PRESSURE CONTROL SYSTEM v Filed Nov. 18, 1946 2 Sheets-Sheet 2 I?m |7 l l6)v J 7 ma I4 46 47 4s 2o I f 30 MB 37 36 l9 1 v 4 I3 38 1! ma 232 as GOQI 59 33 25 i 39 z 23 1 1E 22 5 31 34 IB i 7 21 5 27 25 IN!'L'N'I'OR. JAMES M. KEMPER v ATTORNEY Patented July 4, 19 50 CABINPRESSURE CONTROL SYSTEM James M. Kempcr, Hollywood, Calif., assignor toThe Garrett Corporation, Los Angeles, 021111., a corporation ofCalifornia Application November 18, 1948, Serial No. 710,677

22 Claims.

1 This invention relates generally to means for controlling thepressurized ventilation of an enclosure, and relates more particularlyto means for maintaining a desired ai pressure within the enclosure.

While the invention has particular utility in connection withpressurized ventilation of aircraft cabins and the like, and is shownand described embodied in such an installation, it is to be understoodthat its utility is not confined thereto.

It is sometimes highly desirable to produce a gradual change in the airpressure within an aircraft during its flight from one altitude toanother, as from a lower altitude airport to a higher one, or viceversa, and it is therefore an object of the present invention to providemeans by which the air pressure within a cabin or enclosure may beautomatically changed at a predetermined rate, regardless of the rate ofchange in ambient atmospheric pressure. Thus discomfort or harm to theoccupants of the aircraft is avoided.

It is another object of the present invention to provide means of thischaracter whereby the pressure within an aircraft cabin may be changedat a gradual preselected rate during flight so that it will have reacheda value substantially that of the ambient atmospheric pressure at theterm nal airport. Thus, upon landing at an airport situated at a higheror lower altitude than it lands at said terminal airport, thus avoiding"any sudden and. uncomfortable pressure change at said airport whenlanding and leaving the aircraft.

It is a further object to control the pressure in pressurized cabins insuch manner as will permit the selection of a desired pressure withinthe cabin and also a desired rate of pressure change within the cabinwhereby changes in pressure to which occupants of the cabin aresubjected will not be so abrupt or rapid as to cause discomfort.

Let it be supposed that an aircraft upon leaving an airport at onealtitude is to land at a field of different altitude within a givenperiod of time. The occupants of the cabin are subjected to a pressurechange, produced gradually, so that when the second landing field isreached, the pressure to which the occupants are subjected within theaircraft cabin will correspond to the atmospheric pressure at the secondlanding field.

During the flight from the first field to the second field, although theaircraft may rise to an altitude considerably above the altitude ofeither landing field, the occupants of the pressurized cabin will not beconscious of this fact, but will be subjected to a reduced pressure nogreater than that corresponding to the altitude of the highest of thetwo landing fields.

Another object of the invention is to provide a device of this characterwherein the control means is responsive to a control chamber pressure.

Still another object of the invention is to provide a cabin structureprotective means or supplementary control which functions to relieveexcessive cabin pressure if it should exceed a safe value, based uponthe structural characteristics of the cabin.

It is a further object to provide a device of this character that isrelatively simple in construction and reliable in operation.

Other objects and advantages of the invention will appear from thefollowing part of the specification.

Referring to the drawings, which are for illustrative purposes only,

Fig. l is a diagrammatic view of a control mechanism embodying thepresent invention;

Fig. 2 is a fragmentary view taken on the line line 2--2 of Fig. 1;

Fig. 3 is an enlarged sectional view of the cabin outlet flow controlvalve taken on the line 33 of Fig. 4; and

Fig. 4 is an end view of said valve.

Referring to Fig. 1, there is shown a schematic or diagrammaticrepresentation of a cabin pressure control system embodying the presentinvention. An enclosure or cabin is indicated genorally at III, which issupplied by air under pressure by a supercharger l I, or the like, whichmay be operated by any suitable source of power, not shown, formaintaining a flow of air through the cabin for purposes of ventilation.The cabin is provided with an outlet opening l2 which is controlled byan outflow valve assembly, indicated generally at l3, although it may beotherwise disposed. The valve I3, as herein shown, is an example of onetype which may be used in the present control system and which willdirectly control cabin pressure. Other types of outflow valves may beused, another example being that disclosed in my copending applicationfor a Cabin 'Pressure Regulator, Serial No. 556,790, filed 0ctober 2,1944, now Patent No. 2,463,491.

The valve assembly I3 is best shown in Fig. 3,

and comprises an outwardly opening valve member, indicated generally atl4, and includes a movable wall in the form of a cup-shaped valve havinga body member He and an annular, axially extending wall Nb, and a freeedge Me which is engageable with a sloping seating surface |5a of aseat, indicated generally at IS, in the shape of a truncated cone. Withthis construction of valve member Hi there is no increase in theeffective pressure area of said member as the valve opens.

The valve seat I5 is formed integrally with a base ring l6, which isattached to the cabin by any suitable means, such as bolts, not shown.The base ring and seat extend about the outer end of the opening I! andare provided with a passage therein, which registers with said openingl2. Z-shaped, in cross section, is supported in spaced relationship tothe ring l6 by means of spacer sleeves i9 disposed on bolts'2ll, whichare annularly spaced apart.

The member l8 includes an outwardly extending annular flange 2| havingholes therein for, reception of the adjacent ends of the bolts 20. andinterposed between the flange 2| and the An annular member l6, generallysleeve 20 is an inturned flange 22 Man annular bolts 20, said ends beingthreaded and provided with nuts 26 thereon. As disclosed, a gasket 21may be provided between the flanges 2| and 25 to thereby insure anair-tight seal between said flanges. Additional clamping or securingmeans are provided and comprise bolts 29, which are annularly spacedapart between the bolts 20. Between the side wall Nb of the valve memberMa and an in-turned flange 3| of the member I8, is a flexible diaphragm32 which is of generally cylindrical shape and unresponsive to ambientpressure. One end of. the diaphragm.32 receives the flange-like wall l4bof the valve member l4 in a snug lit, and the opposite end of thediaphragm 32 is inturned and clamped to the flange 3| of the member l8by means of an annular ring-like plate 33 on the side of the diaphragmopposite the flange 3|, the parts being secured together by means ofannularly spaced screws 34. The flange 3| of the member I8 is axiallyspaced from the valve member 4 to permit operative movement of saidvalve member. About the cylindrical portion of the diaphragm 32 isdisposed an annular collar 35;one end of which is secured to the valvemember l4 and diaphragm by means of a press fitted ring or band 36, theother end being-in radially spaced relation to the member l8. To provideadditional securing means between the valve l 4 and the diaphragm 32,the valve member is provided with an annular groove 31 in which aninternal annular flange 38 of the diaphragm is received, therebypreventing axial slippage between the-parts. When the device isassembled the diaphragm 32 includes a generally U-shaped portion 39 inthe space between the member l8 and the collar 35, the latter extendinglongitudinally beyond said U-shaped portion of the diaphragm. The valvemember, diaphragm 32, member l6 and 4 cover 24, define a pressurechamber 46, said chamber 40 being connected by a substantiallyunrestricted conduit 4| with a pressure chamber 42 defined by a housing43 of a control or regulating unit, to be hereinafter described, thepressure within said chamber. 42, conduit 4|, and chamber 46 being thecontrol pressure, and is of substantially the same value throughoutthese parts, said housing being connected to a source of pressure shownas a small, calibrated, restricted bleed connection 42a with the cabin,which provides a small flow of air between the cabin and said chamber42.

The valve member l4 is movable axially and is provided with an axialstem 54 having a flange 35 secured to said valve member by means ofscrews 56. If desired, the screws may have drill holes in the heads forreception of a locking wire 61. The valve stem 48 has a portion of itsfree end disposed within the adjacent free end of a coaxial tubularsleeve or guide 38, which is shown as being integral with the cover 23and which extends into the chamber all, there being cross bores 6| inthe sleeve 68, adjacent its fixed end, forming pressure relief passagesfor the interior bore 4% thereof. v

The sleeve to has an enlarged bore adjacent the free end in which isreceived a ball bearing assembly, indicated generally at 56, andcomprising a bearing housing 55 with ball andrace assemblies 56 and 51disposed therein. The ends of the housing 55 are inturned at 66 and 59,the end 58 resting against a shoulder at the inner end of the enlargedbore of the sleeve. The flanges 56 and 59 also form shoulders whichmaintain the ball and race assemblies in the housing. said ball and raceassemblies being axially spaced apart within said housing to permitoperative movements thereof. The stem 44 of the valve member I4 isreceived within the ball bearin assemblies which provide a substantiallyfrictionless support for said stem, and which move axially within thehousing 56 with axial movements ofv the valve stem 44.

The valve member I4 is urged in the closing direction by a relativelylight spring 60, which reacts between said valve member and a springretainer 6|, operably secured on the sleeve 48 by means of a retainingring 62, which is clipped into a groove provided therefor in said sleeve46.

Referring again to Fig. 1, the control mechanism in the housing ,43,which governs or regulates the control pressure in said housing, isshown as one arrangement of the invention, and it is to be understoodthat other arrangements can be used within the scope of the invention.This control mechanism, as shown, comprises isobaric control means,indicated generally at 65, which, as shown, comprises a bellows 66,pressure rate of change means, indicated generally at 61, and comprisinga bellows 68, which may be a metallic spring bellows, as shown, with apredetermined inherent spring rate and deflection characteristic, or maybe otherwise spring biased in both the collapsing and extendingdirections, as will be apparent to those skilled in the art, anddiflerential pressure control means, indicated generally at 69, andwhich, as shown, comprises a bellows Ill. The bellows 66, 68 and 70 aresecured at one end to a fixed member, which, as

shown, is the bottom wall H of the housing 43.

amass:

a stop 81a disposed within it, having one end fixed adjacent the fixedend of said bellows and having its free end located adjacent the movableend or wall I2 of the'bellows, where it is adapted to be engaged by a,plate 13, which forms part of a shaft or stem 14 extending axially fromthe v free end I2 of said bellows 08.

Altitude preselecting means, indicated generally at I5, is provided andincludes means for applying a variable yielding force tending to extendthe bellows 88. This means comprises a spring a secured at one end tothe free end of Adjustable stop means is provided for limiting theextension of the bellows 60 and, as shown, comprises a bell crank 80pivoted on a pin 8I in an car 82, said car being secured to the adjacentwall of the housing 43. The pivotal pin III is adjacent the junction ofa horizontal arm 84, and a substantially vertical arm 85 of the bellcrank 80. I

The free end of the arm 84 is bifurcated at 88 for reception of the stem14, which has a pin 81 secured therein on the bellows side of thebifurcated end 86. The arm 85 has a recess 88 therein, for reception ofone end of a spring 89 which reacts against the bottom of said recessand the adjacent wall 83 of the housing, to thereby urge bellows 68,said stem 96 being fixed to the movable end or wall 81 of said bellows.

The stems I4 and 96 have pin and slot connections 98 and 99 with therespective ends of the beam 95, which is pivotally secured, intermediatesaid ends, to

the stem I00, a movable valve member I 0|, by means of a pivot pin I02located adjacent the lower end of said valve stem I00. Thus-it will beapparent that the isobaric bellows 66 and the rate of change bellows areconnected together in parallel for operation of the valve IN.

The valve I00 is slidable ina fixed guide I03 which may be secured toany suitable support, indicated generally at I04, said valve member IOIbeing tapered and adapted to cooperate with a valve seat I05 in theadjacent end of a conduit I06, which extends to the outside of thecabin, said conduit forming communication means between the chamber 42of the control unit and ambient atmosphere.

The rate of change control means controls the rate of change of thepressure level in the chamber 42, and hence, in the cabin, and includesa conduit I08 connecting the interior of the bel-,

on the exterior and interior respectively of said bellows.

Means for adiustably controlling the rate of change at a preselectedrate includes the connection II2 having a short tubular member 3 with avalve seat II4 adjacent its free end which is engageable by aconical-shaped movable or adjustable valve member II5 for controllingthe flow of fluid through said connection I I2. The valve member II5 hasa threaded stem I I6 adjustably secured in a boss I I1 integral withadjacent wall II8 of the chamber III, said stem II 8 having a knurledknob II9 thereon, to facilitate adjustment of the valve H5. The purposeof tank I09 is to provide a relatively large volume of air in the fluidcircuit of the rate of change means so that the operative movements ofthe spring bellows 68 to either side of its free or balanced pressureposition extend over a substantial period of time.

-The difierential pressure bellows I0 prevents the pressure in thechamber 42, and hence cabin pressure, from exceeding a predeterminedmaximum, said bellows having its interior connected to atmosphere bymeans of a conduit I20, so that it is responsive to the differential ofpressure within the housing and atmosphere or ambient pressure. Thebellows 10 has a movable end or wall I2I to which is attached to valvestem I22 4 of a conical, movable valve member I23, said stem beingslidablein a, guide I24 attached to any suitable supporting means, suchas indicated generally at I25. The movable valve member I23 'isadaptedto cooperate with the seat I26 formed in the adjacent end of a conduitI21, which connects the chamber 42 with atmosphere. The stem I 22 isconnected by a pin and slot connection I28, to an intermediate part of alever I29 having one end pivotally secured on a pin I30 in an ear I3I,secured to the wall I32 of the housing 43. The opposite end of the leverI29 is provided with a pin I33 to which one end of a spring I34 issecured, the opposite end of said spring being attached to a fixedmember I35, which in turn is attached to the wall I9 of the housing.

Operation.

Normally the pressure on the cabin side of the valve member I4, urgingsaid valve in the opening direction, is balanced by the force of spring60 and the air pressure in the chamber 40. The unbalancing of theseforces will move the valve in the opening direction until thedifferential of pressures on opposite sides thereof will reach a balanceor state of equilibrium. When said valve is in an open'position and thepressure on the inner or cabin side is lower than that on the outerside, the valve will move in the closing direction until seated, oruntil a balance' of pressures on the opposite sides thereof is reached.

It is to be understood that the supercharger I I is operatedcontinuously during a flight at a predetermined rate. This pressuretends to be reduced constantly due to leakage from the cabin and escapeof air through the valve I3 which is at least slightly open when thesupercharger is running. However, other factors being equal,

the valve moves to a more nearly closed position as altitude is gainedand the reverse is true as a plane descends. This is due to the factthat air leaks from the cabin faster as higher altitudes are attained,as the ambient pressure progressively decreases as altitude is gained.Also as altitude is gainedtthe difierential of cabin over'atmosphericpressure increases for a given a lapsing of said bellows. in an openposition.

ansgssavalve opening so that in order to maintain proper cabin pressurethe valve must move in the closing direction with such gain in altitude.

Before a trip or flight begins, and while the aircraft is on the ground,the pressure in the control chamber 42 is at ambient atmosphericpressure, which also exists in the bellows and the tank I09 due to theirconnection with the I chamber 42 through the adjustable vent H2. Thepressure in chamber .40 of the valve unit I3 will also be the same asthat in the control chamber 42 due to its connection 4| therewith.

Assuming the flight is to be from a lower to a higher altitude, thetension of spring 15a is adjusted for the altitude of the destinationairport. In this case the tension of said spring 15a is lessened so thatthe isobaric bellows 86 v is permitted to collapse to the point whereplate I9 engages the fixed stop 61a to limit said col- The valve .I0 Iis then While the aircraft is onthe ground, and with the supercharger IIoperating to provide ventilating flow, the valve member l4 remains inthe open position because the pressure tends to build up within thecabin. This cabin pressure ex- 1 erts a force on said valve greater thanthat exerted by spring 50 plus the pressure within the chamber 40, itbeing understood that the pres- I sure differential required to open thevalve is small due to its large area. Besides adjusting the springtension for th isobaric bellows. the rate valve II 5 is also 'adjustedto the value computed, for the rate, of change for the estimatedduration of the flight.

When the aircraft takes 01! and begins to gain altitude, ambient airpressure drops and air w n escape from the control chamber 42 to atmos-3 phere by way of the conduit I06. as the valve IN is open. Thus thepressure in chamber 42 drops and along with it the pressure in chamber40 drops;

Simultaneously, as the pressure in chamber 42 Air in the bellows 68 andthrough the restricted valve controlled port 2, at a rate determined bythe setting of the rate of change valve H5. As the air escapes from ithe bellows Gland tank I09, said bellows gradually collapses over apredetermined period of time, and moves the valve IOI in the openingdirection. The rate at which said air escapes from the bellows 68 andtank I09 into the cham-.

ber 42 is such that an equilibrium pressure is attained between theinterior of said bellows and chamber 42 by or shortly before the timethe plane reaches its destination airport, at which time the isobaricbellows will have expanded sufllciently to take over control of thevalve IOI, it being understood that at any time the pressure in thecontrol chamber 42 reaches a value corresponding to the setting of thealtitude selecv j tor I5, the isobaric bellows 66 takes over control tomaintain a constant pressure in the cham- 1 her 42. That is, theisobaric bellows 66 expands as the pressure in the control chamber 42 isreto a value predetermined by the setting of the altitude selector I5.

The differential control may be considered as a safety device forholding the cabin pressure 8 at a safe differential relative toatmosphere at high altitudes and prevents bursting or rupturing of thecabin. With this in mind the differential pressure bellows I0 opens thediiferential control valve I23 at a predetermined safe pressure toprotect the cabin structure. Because of the differential bellows, a setdifferential pressure between the cabin pressure and atmosphericpressure will not be exceeded.

In flying from a higher to a lower altitude, the altitude selector knobI6 is adjusted for the terminal airport and is moved in a direction toincrease the force of spring 15 on the isobaric bellows 66, said bellowsbeing expanded to a point whereat the pin 81 in the stem I4 engages thebifurcated end 86 of. the lever 84 which limits the expansion ofsaid-bellows. of-the isobaric bellows effects closing ofthe valve IM andduring the flight from the higher to the lower altitude airport theaction of the device is the reverse from that described in connectionwith a flight from a low altitude airport to a higher altitude airport.I

From the foregoing it will be apparent that the isobaric bellows 6B isresponsive to changes in the control pressure for limiting said controlpressure and thus effecting the'limiting of the cabin pressure level.Therefore, the rate of change bellows is sensitive to the controlpressure for and controls the rate of change of said pressure, thuscontrolling the rate of change of cabin pressure; and the bellows I0 iscontrolled in accordance with the diflferential between the controlpressure and atmospheric or ambient pres- 35 sure.

It will be understood, of course, that the term aircraft as used herein,refers to any device adapted to pass through the earths atmosphere.

I claim:

1. Mechanism for controlling the pressure in an enclosure, comprising:pressure control means operable to control the pressure in saidenclosure, said pressure control means including a movable pressuresensitive element; walls defining a control pressure chamber; saidmovable pressure sensitive control element being exposed on one side tocontrol chamber pressure and on the other side to enclosure pressure;means for regulating said control chamber pressure, including meanssubjected on one side to control chamber pressure and on the other sideto a region of controlled pressure variable at a predetermined ratethrough a calibrated restricted bleed, for gradually varying saidcontrolchamber pressure over a predetermined period of time; and meansfor arresting control chamber pressure at a predetermined value.

2. Mechanism for controlling the pressure in an enclosure, comprising:pressure control means operable to control the pressure in saidenclosure, said pressure control means including a movable pressuresensitive element; walls defining a control pressure chamber having aninlet passage and an outlet passage, said movable pressure sensitivecontrol element being exposed on one side to control chamber pressureand on the other side to enclosure pressure; a fluid reservoir; meanscontrolling the fiuid flow between said reservoir and a region ofpressure of a difierent value than that in said reservoir; and means forcontrolling one p'f the control chamber passages, said means beingresponsive to the differential of pressure between said control chamberand said reservoir for controlling the pressure in said control chamber.

This adjustment 3. Mechanism for controlling the pressure in anenclosure, comprising: pressure control means operable to control thepressure in said enclosure, said pressure control means including amovable pressure sensitive element; walls defining a control pressurechamber having an inlet passage and an outlet passage, one of saidpassages being restricted; said movable pressure sensitive controlelement being exposed on one side to control chamber pressure andadapted to be subjected on the other side to enclosure pressure; apressure responsive device subjected on one side to control chamberpressure for controlling the unrestricted passage; a fluid reservoirhaving a connection with the other side of said pressure responsivedevice and having a connection with said control chamber; and means forcontrolling the last named connection for regulating the flow of fluidtherethrough.

4. Mechanism for controlling the pressure in an enclosure, comprising:pressure control means operable to control the pressure in saidenclosure, said pressure control means including a movable pressuresensitive element; walls defining a control pressure chamber having arestricted inlet and an outlet; said movable pressure sensitive controlelement being exposed on one side to I control chamber pressure and onthe other side to enclosure pressure; valve means for controlling theoutlet of said control pressure chamber; pressure responsive means forcontrolling said valve means, said means being subjected on one side tocontrol chamber pressure; a fluid reservoir having a connection with theother side of said pressure responsive means; means connecting thereservoir with the control chamber; and preselective valve means forcontrolling the last named connection for permitting a gradual pas- Sageof fluid between the reservoir and control chamber.

5. Mechanism for controlling the pressure in an enclosure, comprising:pressure control means operable to control the pressure -.'in saidenclosure, said pressure control means including a movable pressuresensitive element; walls defining a control pressure chamber having aninlet passage and an outlet passage; said movable pressure sensitivecontrol element being exposed on one side to control chamber pressureand adapted to be exposed on the other side to enclosure pressure; meansfor controlling one of.

said passages for controlling the pressure in said control chamber, saidmeans including means sensitive to the absolute pressure in the controlchamber, and pressure responsive rate of pressure change means operableat a preselected rate subjected to control chamber pressure on one sideand to a region of variable pressure on the other side, said region ofvariable pressure having a restricted connection with the controlchamber, and adapted to override the absolute pressure sensitive means;and means for adjusting the response of said absolute pressure sensitivemeans.

6. Mechanism for controlling the pressure in an enclosure, comprising:pressure control means operable to control the pressure in saidenclosure, said pressure control means including a movable pressuresensitive element; walls defining a control pressure chamber having aninlet passage and an outlet passage; said movable pressure sensitivecontrol element being exposed on one side to control chamber pressureand on the other side to enclosure pressure; means for regulating saidcontrol chamber pressure and gradually varying same over a predeterminedpe-* riod of time, including means responsive to varia-' rate; means forarresting control chamber pressure at a predetermined value, said meansincluding a movable wall and being absolutely responsive to the pressurein the control chamber; and means limiting the movement of the wall ofthe absolute pressure responsive means in at least one direction.

7. Mechanism for controlling the pressure in an enclosure, comprising:pressure control means operable to control the pressure in saidenclosure, said pressure control means including a movable pressuresensitive element; walls defining a control pressure chamber. having arestricted inlet and an outlet; said movable pressure sensitive controlelement beingexposed on one side to control chamber pressure and on theother side to enclosure pressure; means for regulating said controlpressure, including adjustable isobaric control means subjected tocontrol chamber pressure and an adjustable rate of change means havingone side subjected to control chamber pressure for controlling saidoutlet; a reservoir having a connection with the adjustable rate ofchange means for subjecting the opposite side of said means to reservoirpressure so that said rate of change means is operable in response tovariations in the differential between control chamber pressure and thereservoir pressure; and

r a restricted connection between said reservoir and control chamber.

8. Mechanism for controlling the pressure in an enclosure, comprising:pressure control means operable to control the pressure in saidenclosure, said pressure control means including a movable pressuresensitive control element; walls defining a control pressure chamberhaving a restricted inlet and an outlet, said movable pres suresensitive control element being exposed on one side to control chamberpressure and on the other side to enclosure pressure; a valvecontrolling said outlet; an absolute pressure responsive bellows withinthe control chamber, said bellows being connected to said valve; stopmeans within the bellows for limiting collapse thereof; adjustable stopmeans for limiting expansion of said bellows; yielding means for urgingextension of said bellows; means for adjusting said yielding means; arate of change bellows within the chamher and connected to said valve,said rate of change bellows having its exterior subjected to thepressure within said chamber; means, in-

cluding a tank, connecting the interior of the last mentioned bellowswith the interior of the chamber; and adjustable means for controllingthe rate of pressure change Within the bellows and tank.

9. Mechanism for controlling the pressure in an enclosure, comprising:pressure control means operable to control the pressure in saidenclosure, said pressure control means including a movable pressuresensitive element; walls defining a control pressure chamber having arestricted mlet and an outlet; said movable pressure sensitive controlelement being exposed on one side to control chamber pressure and on theother side to enclosure pressure; valve means for controlling the outletof said control pressure chamber; pressure responsive means forcontrolling said valve means, said means being subjected on one side.between the reservoir and control chamber; a

second outlet for said chamber; a valve for controlling said outlet; anddiflerential pressure responsive means for controlling said valve, saiddiflerential pressure responsive means being lapsing thereof; adjustablestop means for limiting the expansion of said bellows; yielding means tourge extension of the bellows; means for adjusting said yielding means;a rate of change bellows within the chamber andconnected to the secondmentioned valve, said rate of change bellows having its exteriorsubjected to the pressure within said l-chamber; means, in-

- eluding a tank, connecting the interior of the adapted to beresponsive to the diflerential oi pressure between that in the controlchamber' and ambient pressure. r I 1 10. In a pressure controlmechanism: walls defining a control pressure chamber having an inletpassage and an outlet passage; means for controlling the pressure insaid control chamber comprising a diflerential pressure responsivedevice subjected on one side to pressure .in said control chamber andadapted to control oneo! said passages; a relatively large, capacityconnection between the other side 01' said device and the controlchamber; presettable restricted means ,ior said connection with thecontrol last mentioned bellows with the interior of the chamber; andadjustable means for controlling the rate of. pressure change within thebellows and tank. I Y

14. The invention defined by claim 13, wherein there is a secondconnection between the chamher and atmosphere; a valve controlling saidconnection; a bellows within the chamber, connected 7, to said valve andsubjected on the outside to chamber pressure; and means connecting thesure responsive device in controlling said one pas sage. l

11. In an aircraft cabin pressure control mechanism having means forsupplying air under pressure to the cabin, comprising: flow controlmeans I for directly controlling the cabin pressure including a valvesubjected on one side to cabin pressure for urging said valve in theopening direction and means forming an enclosure whereby said valve issubjected on the other side to a fluid pressure in said enclosure; meansfor.

12. The invention defined by claim 11, wherein said rate oi. changemeans includes-a bellows within the housing; and there is a restrictedcon-' nection, including a reservoir, between the interior of thebellows and the interior oi 'thehousing.

1 3. In an aircraft cabin pressure control system having means forsupplying air under pressure to said cabin, comprising: flow controlmeans for directly controlling the cabin'pressure including a valvesubjected on one side to cabin pressure for urging same in the openingdirection, and means forming an enclosure for subjecting the other sideof said valve to a fluid control pressure; means for regulating saidcontrol pressure including a control chamber having arestricted'connection with the interior of the cabin, a connection withsaid enclosure, and a connection with atmosphere; a valve controllingsure responsive bellows within the chamber, said bellows being connectedto the last named valve;

interior o'f'said bellows with the atmosphere.

15. -Mechanism for controlling the pressure in an enclosure, comprising;pressure control means operable to control the pressure in said enclo-'sure, said pressure control means including a movable pressuresensitive element; walls defininga control pressure chamber; saidmovable pressure sensitive control element being exposed on one side tocontrol chamber pressure and on the other side to enclosure pressure;means for regulating said control chamber pressure, including meanshavinga-limited rate of movement and responsive to variations in thedifierential oi pressure between that in the control chamber and aregion of controlled'pressure, for gradually varying said controlchamber pressure over a predetermined period of time; adjustable meansfor controlling the rate of change of the pressure of said region; andmeans for arresting control chamber pressure at a predetermined value.

16. Mechanism for controlling the pressure in an enclosure, comprising:pressure control means operable to control the pressure in saidenclosure, said pressure control means including a movable pressuresensitive element; walls defining a control pressure chamber having aninlet passage and an outlet passage; said movable pressure sensitivecontrol element being exposed on one side to control chamber pressureand on the other side to enclosure pressure; and means for regulatingsaid control chamber pressure to gradually vary same over apredetermined period of time, said means including means responsive tovariations in the differential of presmovable pressure sensitiveelement; walls definsaid atmospheric connection; an absolute presing acontrol pressure chamber; said movable pressure sensitive controlelement being exposed on one side to control chamber pressure and on theother side to enclosure pressure; means for regulating said controlchamber pressure, including a pressure responsive device having amovable wall operable at a controlled rate of response and responsive tovariations in the differential of pressure between that in the controlchamber and a region of controlled pressure,said region having aconnection with the control chamber for gradually varying said controlstop means within the bellows for limiting col- 1| chamber pressure overa predetermined period 13 I of time; and means for arresting controlchamber pressure at a predetermined value.

18. Mechanism for controlling the pressure in an enclosure, comprising:pressure control means operable to control the pressure in saidenclosure, said pressure control means including a movable pressuresensitive element; walls defining a control pressure chamber; saidmovable pressure sensitive control element being exposed on one side tocontrol chamber pressure and on the other side to enclosure pressure;and means for regulating said control chamber pressure, including meansexposed on oneside to pressure in the control chamber and on the otherside to a region of controlled pressure having a restricted connectionwith the control chamber and operable independently of atmosphericpressure, for

gradually varying said control chamber pressure over a predeterminedperiod of time.

19. In a pressure control mechanism: walls defining a control pressurechamber having an inlet passage and an outlet passage; means forcontrolling the pressure in said control chamber comprising adifferential pressure responsive device subjected on one side topressure in said control chamber and adapted to control one of saidpassages; a connection between the other side of said device and thecontrol chamber, said connection including a relatively large capacityportion interposed therein; means forming a restriction between saidlarge capacity portion of the connection and the control chamber; and anabsolute pressure responsive device subjected to control chamberpressure adapted to cooperate with the differential pressure responsivedevice in controlling said one passage.

20. In a pressure control mechanism: walls defining a control pressurechamber having an inlet passage and an outlet passage; means forcontrolling the pressure in said control chamber comprising adifferential pressure responsive device subjected on one side topressure in said control chamber and adapted to control one 01' saidpassages; a connection between the other side of said device and thecontrol chamber, said an enclosure, comprising: pressure control meansoperable to control the pressure in said enclosure, said pressurecontrol means including a movable pressure sensitive element; wallsdefining a control pressure chamber; said movable pressure sensitivecontrol element being exposed on one side to control chamber pressureand on the other side to enclosure pressure; means for gradually varyingthe control chamber pressure, including pressure responsive meansresponsive to the differential of pressure between that in the controlchamber and a region of variable pressure; and means for controlling therate of pressure change in said region.

22. In a pressure control mechanism: walls defining a control pressurechamber having an inlet passage and an outlet passage; means fordirectly controlling the pressure in said chamber including adifierentlal pressure responsive device subjected on one side topressure in said control chamber adapted to control one of saidpassages; a connection between the other side of said device and thecontrol chamber, said connection having a relatively large capacityportion therein; and means forming a restriction between said largecapacity portion of the connection and the control chamber.

connection having a. relatively large capacity portion interposedtherein; and means forming a restriction between said large capacityportion of the connection and the control chamber.

21. Mechanism for controlling the pressure in JAIWES M. KEMPER.

REFERENCES CITED The following references are of record'in the file ofthis patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain Aug.21, 1944 Number 2,393,343 2,396,116 2,399,326 2.407.258 2,413,0272,424,491 2,441 ,592 2,463,487 2,463,489 2,463,490

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